The present invention is directed to a finishing apparatus for an image producing device, and more particularly, to a signature booklet maker (SBM) having a modified fold blade and a trim waste elimination device.
A "signature" is a duplex printed copy sheet having two page images on each side. The signature sheet can be folded in half to form a booklet or a plurality Of signatures can be aligned, stitched together, and folded in half to form a multi-sheet booklet. A description of signature printing is provided in U.S. Pat. No. 4,727,402 to Smith, the disclosure of which is incorporated herein by reference.
The SBM can be constructed, for example, from variants of three existing finishing modules such as the AGR/Automatic Stitcher, the PA/Automatic Folder, and the TR/Automatic Trimmer, manufactured by C. P. Bourg for off-line use. All modules require mechanical modification to support front edge registration vs. center registration and wiring modification to share basic signals with the printer. The printer exports sheet arrival times and end- of-set signals to the SBM equipment. The first module receives and aligns the copy sheets in a set (which set forms a single booklet) so that all sheets in the set are aligned with one another. The first module aligns each sheet by stopping the forward movement of the sheet (e.g., with a gate or sheet stop), and then laterally tapping each sheet against another sheet stop. Once all sheets in the set are received and aligned, the first module stitches or binds all the sheets in the set to each other at a central location (between each page image on each sheet). The stitching step can comprise, for example, stapling. Thus, the first module is referred to as a "saddle stitcher."
The stitched copy set is then forwarded to a second module which folds the stitched copy set in half about the stitch axis. Thus, the second module is referred to as a "folder."
The folded copy set is then forwarded to a third module where the edges of the sheets opposite from the fold are trimmed. Thus, the third module is referred to as a "trimmer." Trimming is necessary, particularly in large sets or booklets, because the edges of the sheets opposite from the fold become uneven after folding.
A problem arises in the folding module in that the direct contact of the fold blade and the stitches often cause the occurrence of fold skew (i.e., the stitches fall on either side of the fold blade) and inside sheet marking. These problems have a significant effect on the final appearance of the booklet. Moreover, as a result of fold skew, when the booklet is transferred to the trimming module, the pages are then trimmed in an uneven manner.
Another problem arises in that static electricity on the sheet output can cause major problems in the machine performance throughout the signature booklet maker. Namely, the booklet trimmings adhere to the sheet affecting the final output and causing paper jams. Still further, it is difficult to keep booklet trimmings from migrating throughout the trimming module. The migration of trimmings causes false shutdowns at jam switches and trim waste on the exit conveyer and inside booklets.
Yet another problem with the existing signature booklet maker arrangement arises in that the upper knife assembly of the trimming module is exposed and can be a significant safety hazard for the operator.